A fiber optic connector for connecting an optical fiber to an optical fiber of an other fiber optic device usually includes an alignment ferrule. The fiber optic connector typically utilizes the precise dimensions of the alignment ferrule to align with precision the optical fiber therein with the optical fiber of the other mating fiber optic device. Alignment ferrules often include a high precision front section that is concentric with a central passage in which the optical fiber is held, whereby orientation of the front section also orientates the corresponding optical fiber. In producing such a precision portion, the outer cylindrical wall of the high precision front section is usually used as datum to define the concentric central passage with precision and in a cost efficient manner. A lower precision body portion is often used to incorporate the alignment ferrule into the fiber optic connector. These ferrules may be used either singularly or in conjunction with others.
Alignment ferrules have been manufactured using a variety of methods to achieve the high precision at the front section, while realizing cost savings through the lower precision requirements of the body portion. U.S. Pat. No. 4,634,214, for example, discloses a two-piece ferrule where the front section is a cylindrical ceramic piece that is frictionally fit or bonded within a collar of a lower precision rear section.
U.S. Pat. No. 5,013,122 discloses a ferrule that is made from metal or thermoplastic material having the high precision front section and the body portion integrally formed. A bipartite ferrule may also be produced by attaching the front section to the rear body portion through the use of mechanical means, such as threads or bosses, or through bonding means, such as the use of heat, ultrasonic, or adhesive techniques. A ferrule made from injection molded plastic is disclosed in U.S. Pat. No. 4,834,487. This is a one-piece ferrule that has a precision front section and a body portion formed such that the precision front section is free of molding flash.
The ferrules disclosed in the above patents have a number of drawbacks for high volume production. Although the one-piece ferrules have the necessary structural integrity, their production processes are limited by the high precision required at the front section. The two-piece ferrules allow the manufacturing process and materials selection to be tailored to the particular sections of the ferrule, allowing for optimization of the manufacturing process. However, the two-piece ferrules require joining features, such as threads, bores, or bosses, be incorporated. These additional features can impose the same precision requirements on the rear body section that were trying to be avoided.
U.S. Pat. No. 5,375,183, on the other hand, discloses an overmolded alignment ferrule that may be produced economically and in high volume, while taking advantage of the different precision and material requirements of the front section versus the rear body section and still maintaining the precision required at the front section so that the optical fiber therein may be reliably coupled to the fiber optic device. The overmolded alignment ferrule of this invention may be used in fiber optic connectors to couple an optical fiber therein to an other fiber optic device.
The overmolded alignment ferrule of the '183 patent has a preformed precision portion having a front section for aligning the optical fiber therein with the fiber optic device, and an overmolded body portion configured for incorporating the alignment ferrule into the fiber optic connector. The precision portion also has a rear section, rearward of the front section, having an anti-displacement feature thereupon and d central passage extending therethrough for positioning the optical fiber concentrically with the front section. The body portion also extends rearwardly from the precision portion and is configured to incorporate the alignment ferrule into the particular connector. The body portion has a fiber receiving opening in communication with the central passage of the precision portion to guide the optical fiber thereto.
Even though the device of the '183 patent is a significant improvement over the prior devices, it has some limitations. For example, the geometry of the high precision portion may be limited because, as with prior devices, the high precision portion is produced by using its cylindrical outer wall as datum for defining with precision the fiber channel or bore, which extends concentrically with the outer wall. Accordingly, it would be difficult to modify in a cost-effective way the '183 device to accommodate more than one fiber channels or any other channels.
Accordingly, it is an object of the present invention to provide an overmolded alignment ferrule for aligning a plurality of optical fibers with a mating fiber optic device.
It is a further object of the present invention to provide such an overmolded alignment ferrule including a precision portion having guide pin channels defined therein that are used as datum for defining fiber channels therein with precision and preferably without reliance upon any external datum of the precision portion.
It is a further object of the present invention to provide such an alignment ferrule that enables core pins to be used in producing the precision portion that are relatively short and therefore better able to minimize deflection of the core pins during the molding or other production process. It is a further object of the present invention to provide such an alignment ferrule wherein the precision portion can be produced with a minimal amount of material.